A former Labour MP's researcher and a civil servant were released on police bail last night after being charged under the Official Secrets Act with a "damaging disclosure" of a foreign policy document from the Cabinet Office.

Though officials were saying little last night about an investigation that has been under way for more than a year, initial indications suggested it related to documents on the Iraq war that found their way into a national newspaper.

Leo O' Connor, 42, a former researcher for the Labour MP for Northampton South Tony Clarke, who lost his seat at the general election, was charged with having received a document "through its disclosure without lawful authority by a crown servant".

The man accused with him, David Keogh, 49, is a former communications officer at the Cabinet Office, who was on secondment from the Foreign Office at the time of the alleged offence in April or May last year. He was was charged with making a "damaging disclosure of a document relating to international relations" without lawful authority.

Both will appear at Bow Street magistrates' court, central London, on November 29.

They were arrested last summer after Mr Clarke, 42 whose political interests include Middle East affairs, found the document in his constituency office in Northampton and reported it to the police. Special Branch officers were called in. For several years the Cabinet Office has been plagued by leaks, mostly of Foreign Office papers, and not evidently motivated by politics. Some arrests have been made, up to now without charge.